1. Field of the Invention
The present invention relates to a rotor and a motor.
2. Description of the Related Art
In the conventional practice, motors are used as driving sources of various types of apparatuses and products. For example, the motors are used for business machines, such as printers and copying machines, various kinds of home electric appliances, and power assist sources of vehicles, such as automobiles and power-assisted bicycles. In particular, brushless motors are sometimes used as the driving sources of movable parts with high operation frequency in the light of increased durability and reduced noise.
Known as a type of such a brushless motor is an interior permanent magnet (IPM) motor where a permanent magnet is embedded in a rotor. For example, there is an electric motor in which a plurality of plate-like magnets are radially embedded in a rotor yoke and also each magnet is disposed such that the same poles of adjacent magnets face each other circumferentially (see Japanese Patent 3425176).
While it is an idea to use a magnet with high residual magnetic flux density in order to improve the average magnetic flux density in an outer circumferential part of the motor's rotor yoke, it can disadvantageously lead to an increase in the cost.